Tuning device ratchet



Sept. 14, 1948. w, Y 2,449,079

TUNING DEVICE RATCHET Filed Jan. 7, 1944 3 Sheets-Sheet 1 Sept. 14, 1948. 2,449,079

R. w. MAY

TUNING DEVICE, RATCI-IET Filed Jan. 7. 1944 A? ZQQJ 3 Sheets-Sheet 2 wm/zajgg;

Sept. 14, 1948. R. w. MAY 2,449,079

TUNING DEVICE RATCHET Filed Jan. 7,. 1944 s Sheets-Sheet :5

Patented Sept. 14, 1948 UNITED STATES PATENT OFFICE TUNING DEVICE RATCHET Richard W. May, Cedar Rapids, Iowa, assignor to Collins Radio Company, a corporation of Iowa Application January 7, 1944, Serial No. 517,408

8 Claims. (Cl. '74-10) rotatable cams cooperating with each of a plurality of pawls; another feature of this invention is that the drive connection instantly provides rotation of the driven part upon rotation of the driving part in one direction, this conne-ctoin being capable of transmitting high torque; yet another feature of this invention is that the connecting means provides a connection transmitting low torque, but only low torque, in the opposite dlrection of rotation of the driving part; still another feature of this invent-ion is that, in one form, the first-mentioned connection is released after a brief intervalof rotation and a second drivin connection completed which positively syncho-- nizes the driven part with the driving means; and a. further feature of this invention is that it provides means for instantly disengaging a portion of a pawlfrom a cooperating slot upon initiation of operation of the shaft positioning device, yet ensures accurate and, in one form, positive synchronization of certain of the rotatable parts. Other features and advantages of this invention will be apparent from the following specification and the drawings, in which:

Figure 1 is a side elevational view of a shaft positioning unit embodying this invention, with a portion broken away, along the line I-l of Figure 2; Figure 2 is a plan view of such a unit, with a small part of one of the posts broken away; Figure 3 is a transverse sectional view along the line 33 of Figure 1; Figure 4 :is another transverse sectional view along the line 44 of Figure 1; Figure 5 is a fragmentary view of a portion of the device, with part of the ratchet broken away; Figure 6 is a vertical sectional view of theratchet, along the line 65 of Fig-ure 4; Figure 7 is a fragmentarydetailed sectional view of the ratchet pins, along the line 1-- of Figure 6; Figure 8 is a detailed sectional view along the line 8'8 of Figure 6; Figure 9 is a view similar to Figure 8, but with the ratchet parts in a different position; Figure ld is a transverse sectional viewsimilar to Figure 3, but of another form of a shaftpositioning unit embod i g this invention; Figure. 1.1 is a partial transverse sectional view similar to Figure 4, but of this other form, along the line lll l of Figure 12; Figure 12 is a fragmentary elevational view, partially broken away, of the ratchet; Fig,- ure 13 is a sectional view along the line l3-l3 of Figure 11; Figure 14 is a schematic view of the stopping combination parts in one position; Figure 15 is a schematic view of the same parts in another position, during homing operation of the unit; and Figure 16 is a schematic view of the parts in stopping position.

The connecting mean which is the subject matter of this application was particularly designed for use in automatic shaft positioningdevices enabling automatic selection of the positions of the tuned shafts of radio apparatus, such devices being shown in a number of previous patents of Arthur A. Collins, as for example Patent No. 2,285,414 which issued June 9, 1942. In automatic tuning devices of this type the tuning ele-: ment shaft carries or is connected to a drum carrying a plurality of stop rings, the arrangement being such that the stop shoulders of these rings can be set at any desired predetermined point. A plurality of pawls are provided adjacent the stop ring drum, one being adapted to cooperate with each stop ring to provide a plurality of stop assemblies, each being adapted to stop the shaft by engagement of the stop shoulder with the cooperating pawl. In operation, a drive motor operates through a drive shaft to rotate the stop rin drum until the drum has reached a terminal position usually termed the home position, the drive shaft then rotating further until a selector cam drum and a selector switch, also driven by it, reach a position corresponding to the electrical circuit selected. Thereupon the drive motor reverses and the drum and tuning shaft are driven in the other direction until the operative pawl (selected by the position in which the selector cam drum stopped) engages the stop shoulder of its cool erating ring, whereupon the tuning shaft is stopped at the desired position; but the drive metor and drive shaft continue until they have completed their cycleof operation, controlled by a limit switch.

When the drive motor reverses, and the tuning shaft is driven in the other or tuning direction, the selector cam drum must remain stationary in the position corresponding to the stop assembly desired to be operative for the particular tuning operation. It will thus be apparent that the selector cam drum must be rotated in the homin nection must be ineffective in the opposite direction of rotation. Accordingly, some form of ratchet or uni-directional drive mean must be employed as a connection between the selector cam drum and the main driving means.

For reason-s which will become apparent during the description of the device and its operation, it is desirable that the driving connection instantly become effective upon initiation of operation of the driving means in the homing direction; yet, in order that a given circuit will always select a given stop combination, it is necessary that the selector cam drum be synchronized in a certain relationship with the driving means before the selector switch becomes effective. I have developed and am here disclosing and claiming ratchet mechanism which accomplishes-these functions with a, minimum number of parts, which is easily manufactured and assembled and which has proved satisfactory in operation, and which is particularly adapted for use in automatic tuning apparatus of the kind disclosed herewith.

In order to describe the operation and advantages of this improved connection, it is necessary to at least briefly describe the construction and operation of the shaft positioning unit in order to bring out the structural environment in which this ratchet mechanism has proved 'so advantageous. The particular shaft positioning unit shown is an improvement in certain mechanical respects over the unit shown and described in the aforesaid Collins Patent No. 2,285,414; and the improvements disclosed herein, other than the ratchet which is the subject of this application, are being claimed in the co-pending application of Arthur A. Collins, Serial No. 472,717, filed January 18, 1943. The way in which a number of such shaft positioning units can be associated to simultaneously tune various shafts of a radio, the drive means and drive shafts therefor and an operative electric circuit for effecting the desired sequence of operations, have all been fully shown in the aforesaid Collins Patent No. 2,285,414, and accordingly have not been illustrated here. Moreover, since the details of construction and operation of such units have been gone into fully in that patent and in the above-mentioned Collins application, an attempt will be made to keep the present general description as brief as is con- 'sistent with providing a good background for the understanding of this improved ratchet connection.

Referring now more particularly to Figures 1-4, it will be seen that the various parts adapted to effect automatic tuning of the shaft of a condenser or other tuning element, as the shaft H), are arranged in a self-contained unit mounted between the end plates II and I2 held in appropriate relationship by the posts 1'3. A drum I4 is fixedly mounted on the shaft Hi, this drum having a longitudinally but non-rotatably movable forward portion Ma adapted to be moved longitudinally of the shaft by means operative by a manually rotatable bar IS on the face of the tuning dial [5. The drum carries any desired number (here shown as eleven) of tuning stop rings, these being here identified as Ila-41k. Appropriate non-rotatable spacer washers are provided between these stop rings, both the rings and washers being axially movable on the drum. When the end portion Ma of the drum is moved to the left (speaking with respect to the position of the parts as shown in the drawings) the stop rings are loosened and may be individually set to desired positions; and when the end portion Ma and serves to transmit pressure from the 'stud I511 to the drum portion Ma, when it is desired to clamp the stop rings in operative position.

A plurality of tuning positioning pawls l8ak and a manual operation pawl Him (the operation of said manual operation pawl being disclosed in the aforementioned Collins application No. 472,717) are provided, the shape and location of the pawls being best seen from consideration of the pawl IBb shown in Figure 3. Each pawl has its operating end urged toward the cooperating stop ring by one of a similar number of springs l9. When a pawl is rendered operative by the selector mechanism to be described, its end drops and rides upon the cooperating stop ring until the slot is reached, whereupon the end drops into the slot and stops the ring (and thus the tuning element shaft ID), as may be best seen in Figure 3. Stopping of the stop ring drum M at either of its two terminal positions, 360 apart, is efected by cooperation between a terminal stop pawl 20 and a stop shoulder 2Ia on a terminal stop ring 2|, this ring being keyed to the drum.

Rotation of the stop ring drum is effected by a drive motor and line shaft having driving connection (through a worm or other appropriate gear, not shown) with the gear 22, this gear being mounted co-axially with the shaft [0, but freely rotatable with respect thereto. It is rigidly connected to a gear 23 which operates, through an appropriate idler gear shown in Figure 5, to drive the gear 24 mounted on the driving part of the ratchet mechanism which is the subject matter of this application. This ratchet provides a one-way driving connection for rotating the selector cam drum carrying a plurality of tuning position selector cams 26ak: and a manual tun ing selector cam 2 6m. These cams are 12 in number, and have depressions in their peripheries, the arrangement being such that the depressions are equally spaced (as may be best seen in Figure 3) so that they form a helix around the selector cam drum. The selector cam drum is rigidly mounted on a shaft 21, the other end of this shaft (as may be best seen in Figure 1), making a lost motion connection (through arms 28 and 29 and pin 30) with the central or rotatable member 3| of the selector switch or tap switch indicated in general as 3-2.

In operating the device to automatically select a new tuning position, the operator selects'a certain circuit by a manually rotatable switch, a telephone type dial switch, or any appropriate means. A motor relay starts the drive motor and drives the gear 22 in a direction such as to rotate the drum counterclockwise (as it is viewed in Figure 3) until it is stopped in terminal position by engagement between the stop shoulder 2m and the stop pawl 20. The drive then continues, further rotating the selector cam drum and selector switch, until the rotatable switch arm of the selector switch reaches the contact or tap corresponding to the selected circuit, whereupon the circuit is opened and relay operation causes the motor to reverse. The drive is then in such a direction that the stop ring rotation is clockwise (as viewed in Figure 3), the selector drum being left standing at the selected position through idling action of the ratchet, this ratchet being operative to drive the selector cam drum only in the first-mentioned direction. When the selected stop combination reaches the position shown in Figure 3, the stop ring drum and tuning element shaft ID are positively stopped by engagement of the stop shoulder with the pawl, the motor continuing until a limit switch finally stops it.

This over-running action of the drive at both ends of the movements of the stop ring drum requires the interposition of a slip-clutch between the drive means and the stop ring drum, this clutch being here identified in general as 33. Drive is effected from a stud 33a carried by the gear 22 and adapted to engage either end of an annular shoe 33b on a clutch drum mounted on the shaft I0. While the device would be operable with any conventional frictional slip-clutch, the shoe-and-drum clutch has certain particular advantages and is the subject matter of the patent to Arthur A. Collins, No. 2,409,192, which issued October 15, 1946.

In order to facilitate setting of the stop rings to new positions, the stop ring slots are doubleshouldered as may be best seen in Figure 3. That is, the two edges of the stop ring slots are radial, these being here identified as I'Ib and 17b"; and this slot'is adapted to receive and cooperate with the stop end or stop portion I81) of the pawl. When it is desired to set one of the stop ringsto a new position to provide a different shaft position for the same stop combination, the switchis first energized to render operative this particular stop combination, so that at the end of a cycle of operation the stop combination is as illustrated in Figure 3. It is then only necessary to loosen the stop rings by rotating the bar l5, whereupon the dial [6 can be used to rotate the tuning shaft l0 the particular stop ring (as the ring I'lb) being kept from rotation by engagement of the end l8b' of the pawl with one or the other of the two sides of the stop ring slot. Since the slot is doubleshouldered, initial movement of the dial toward the new position can be clockwise or counterclockwise, whichever is shortest, and it is only necessary that the final movement be in, a clock- I wise direction, so that the end of the pawl [8b is incontact with the slot shoulder or edge l'lb.

Since the stop ring slot is double-shouldered, some means must be provided for lifting the stop end of the pawl out of its cooperating slot when a new tuning cycle is initiated. It will be noted that the pawl l8b has a portion IBb. adapted to be received by the slot in its cooperating selector cam (as the slot in the cam 26b shown inFigure 3) in order to let the other end of the pawl come into stopping position. Advantage is taken of the cooperation of the selector cam with this other portion of the stop pawl, and the slot in the selector cam is provided with one radial edge, here identified as 261), and one inclined or sloped edge here identified as 2612". Rotation of the selector cam drum in a counterclockwise direction (speaking with respect to the parts as shown in Figure 3) upon initiation of another tuning cycle .opcrates, through cooperation between the inclined edge 2617' with the adjacent portion of the pawl l8b, to lift the other end of the pawl up with the slot in the stop ring llb. This operation must be effected instantly upon initiation of a newtuning cycle if the pawl end is to be retractedbefore it engagesthe stop ring slot shoulder llb", since the drivemeans forthe unit starts rotation of the tuningshaft l0 and stop ring drum at the same time that it starts rotation of the selector cam drum. Y

It will be apparent that the ratchet connection between the gear 24 and the shaft 21, therefore, mustbe'instantly operative upon initiation of drive in the homing direction. Yet, if the same circuit is to always select the same stop combination in a plurality of stop units operated from a single selector switch (as is the case in practice) some means must be provided ior'synchronizing the position of the selector cam drums in the various units withrespect to the drive means. In the particular device disclosed in Figures 1-9, this synchronizingis accomplished by rendering the initial driving connection inoperative after a briefinterval of rotation and allowing a positively operative single -tooth ratchet to effect the synchronized drive. In the device disclosed in Figures 10-46, this is accomplished upon reversal of the drive, and suflicient synchronization maintained thereafter, upon initiation of another tuning operation, by the relatively instantaneous operation of the ratchet mechanism.

Referring now more particularly to Figures 4-9, the double-ratchet drive, indicated in general as 40, will be more particularly described. The gear 24 is rigidly mounted on and rotates with it the driving part H. Concentric with and adjacent to this driving part is a. driven part 42, this being mounted on and rotating the shaft 21 carrying the selector cam arrangement. As may be best seen in Figure 6,these two parts have ad-' jacent cylindrical outer surfaces of the same diameter, the surface on the driven part 42 being of greater length than that on the driving part. Surrounding'these surfaces'and in frictional en'- gagement therewith are the turns or coils of a. closely wound helical spring 43, this spring having a greater number'of turns (here shown as five in number) in engagement with the surface of the driven part than it has in engagement with the surface of the driving part (here shown as only about 2 turns). The springis wound in such a direction that when the driving part rotates counterclockwise (speaking with respect to the parts as shown in Figures 8 and 9), the homing direction of drive, the friction between the driving surface and the spring tends to draw the turns closer into engagement with the two surfaces. This causes the driving part to instantly effect similar rotation of the driven part upon initation of a tuning cycle, as is desired in order to immediately rotate the selector cams and throw the pawl in th particular stop combination which was last operative out of engagement with its corresponding stop rin'g.

The parts are initially in a position as illustrated in Figure 8, and as soon as the parts have rotated enough to bring the end 43a. of the spring into engagement with the post l3c, this initial frictional driving connection is rendered inoperative. That is, engagement of the end 43a with the post [30, which forms a stopping member for this purpose, loosens or slightly unwinds the first few turns of the spring, permitting the driving partto slip Within the spring. That is, as soon as the driving part has rotated the relatively few degrees (10-20 degrees) necessary to go from the position shown in Figure 8 to the position shown in Figure 9, the spring is no longer effective as a driving connection. In order to accomplish this unwrapping action when the end 43a of the spring strikes the post I So, the covering cylindrical shell 44 is providedv with a fairly'long slot 44a. This shell is not connected to either of the parts 4| or 42, but is merely guided between appropriate shoulders on such parts; and always remains in a given relation to the spring, the short end 43b of the spring being turned up and projected through a very small opening in the shell 44.

As may be best seen in Figures 6 and 7, the parts 4| and 42 are also adapted to be connected by-asingle-tooth ratchet comprising the pins 45 and 46. The pin 45 is rigidly mounted on the part 4|, and provided with a sloping face adapted to cooperate with the end of the other pin. The other pin 46 is longitudinally movable in an opening or bore 42a in the driven part 42, the pin being urged to the right by a spring 41. It will be immediately apparent that when the driving part is rotating clockwise, the pins will merely idle or slip by each other; but when the drive part is being rotated counterclockwise, the shoulder on the end of the pin 45 will engage the side of the pin 46 and effect positive driving connection between the parts. Since there is only a single such position possible. with a single pair of pins, this positively operated driving connection will always provide a predetermined relationship between the driving and driven parts, and this ensures proper synchronization of the selector cam drum with the driving means.

Again referring to- Figures 8 and 9, it will be seen that at the beginning of a tuning operation, the parts are as shown in Figure 8. Upon clockwise rotation of the driving part 4|, as has been sition with one end in the slot of its corresponding stop ring. Immediately after this has been done, the end 43a of the spring strikes the stop member or post I30, as shown in Figure 9, and the frictional connection is no longer capable of providing the torque required to rotate the selector cam drum against the resistance of. the cooperating pawls. The driving part 4| thereupon rotates (but without efiecting rotation of the driven part and selector cam drum) until the pin 45 has reached the position shown in dotted lines in Figure 9, engaging the pin 46. Thereupon the positively operative connection comes into action and rotates the two parts, both the driving and driven parts of the ratchet mechanism slipping within the spring 43.

When the end of the drive in the homing direction has been reached, and the drive has been stopped at a position determined by the selector switch with the desired selector cam slot beneath the cooperating portion of its corresponding pawl, the motor reverses and the driving part 4| is driven in the opposite or clockwise direction. The end 43a of the spring thereupon backs away from the post l3e, the spring providing the low torque connection in this direction operative until the pawl has dropped down into the position shown in Figure 3, with its end I81)" in engagement with the shoulder 26b of the selector cam slot, usually only a matter of ten or fifteen degrees. This positive engagement then stops further rotation of the selector cams, the low torque connection ensuring maintenance of the cam and paw] in the relation shown in Figure 3.. The drive means continues operation until the stop ring has been stopped by engagement of its stopping shoulder with the end of its cooperating pawl, the tuned shaft and stop rings remaining in this position while the drive continues (by virtue of the slip-clutch 33) until the cycle is completed by a limit switch. This leaves the parts in a position such as that shown in Figure 8, for example, ready for the next tuning operation.

Inasmuch as the position in which the driving part stops at the end of a cycle of operation is a function of the limit switch, the positions of the pins 45 and 46 may be anything within their circle of revolution. It might only require a few degrees for the pin 45 to engage the pin 46 upon the next operation, it might require or thereabouts (as shown in the drawings), or it might require nearly a full 360. In a situation approaching this latter case, the positively operative drive means would not retract the pawl before its stopping end had come into engagement with the back shoulder of the stop ring slot; and it is for this reason that it is desirable to supplement the positively synchronized drive with the instantly operating spring drive which causes immediate retraction of the pawl upon initiation of the cycle of operation, then becomes inoperative to permit the single-tooth ratchet or positively synchronizing ratchet drive to come into operation.

Another form of this invention is illustrated in Figures 10-16, the remainder of this specification being directedto such figures. The single turn shaft positioning unit illustrated in these latter figures is inall major respectsv identical with the unit which has just been fully described and which is shown in Figures 1-9. Accordingly, the figures were not repeated in their entirety, it being understood that a side elevational view and a top plan view of this latter unit would be the same as the views of Figures 1 and 2 in connection with the earlier described unit. Moreover, the parts in this second form of this invention have been numbered in correspondence with those in the previously described unit, so thatit is felt unnecessary to again describe the general operation of the unit fully. Parts in this second form bear identification numerals which are higher by 40 than the numbers applied to the same part in the first unit; that is, the stop ring 571) in this second form corresponds to the stop ring Hb in the first described unit, the pawl 58?) corresponds to the pawl l8b, the selector cam 66b corresponds to the selector cam 25b, etc.

The principal diiference in this second form of the invention is the provision of a particular slot shape in the selector cam, and the omission of the positive single tooth ratchet, the spring ratchet and slot shape cooperating to give the desired operation of the unit.

In this form of the invention, as may be best seen in Figure 13, the driving part BI and driven part 82 are solid, without the slots and grooves associated with the single tooth ratchet. Part of the outer surfaces. of the driving and driven parts are adjacent coaxial cylinders with the helical spring 83 encircling and at least partly wrapped around each of these parts. As before, a large number of turns is wrapped around the driven part 82, and a smaller number around the driving part 8|; and the direction of winding of the spring is such that it provides a positive or high-torque drive when the driving part is rotating counter-clockwise (speaking with respect to Figure 11), in the first or homing direction of operation of the unit. The operation of the 9 spring is such, however, that itprovides a lower (but appreciable) torque connection between the driving and driven parts when the driving part is rotating in the. other directiomafter reversal of the motor.

As may be best seen in Figure 10 and the schematic views (Figures 14-16), the selector cams, as the cam 65b, are provided with slots which are only slightly wider than the cooperating portions of the pawls, as the portion 58b" of the pawl 58b. Moreover, one side of the slot, as the side 6612', is undercut; and the other side of the slot, as the side 66b" slopes outwardly at about a 45 angle with respect to the, radius intersecting the lower end of this side.

The combination and arrangement of the cam slot and cooperating portion of the pawl, together with the drive connection which provides a high-torque connection in one direction and a low-torque connection in the other, has several advantages in a shaft positioning unit of this type. As may be best seen in Figures 14, 15 and 16, the operating end 58b of the pawl does not pound on the stop ring during operation of the unit in the homing direction, and cannot accidentally cause temporary stopping of the tuning shaft during this homing portion of the cycle.

If it be assumed that some other stop combination has been operative, the stop combination comprising the ring 51b, the pawl 58b and the selector cam 66b would be as illustrated in Fig-- ure 14; Initiation of operation of another tuning cycle would cause rotation of the selector cam 66b in a counter-clockwise direction, as illustrated in Figure 15, this being the high-torque direction of drive. Because the side 65b of the slot is undercut, the cooperating end 58b of the pawl only slightly rops down into the slot during this homing operation, the other side 66b" catching the end of the pawl as soon as it starts to drop. Accordingly, the closest the operating end 581) of the pawl gets to the stop ring, in the homing direction of operation, is as illustrated in Figure 15; and itwill be seen that this leaves a slight clearance between the end of the pawl and the stop ring 511) so that there can be no chance of accidental stopping or anydam-age to the pawl end or stop ring by undesirable pounding together during homing operation. On the other hand, if it be assumed that the stop combination illustrated is the one selected in the particular tuning cycle being described, operation of the selector switch stops the parts in the position illustrated in Figure 15, and the motor thereupon reverses and the selector cam is driven (with a low-torque drive) in the other or clockwise direction, as illustrated in Figure 16. Be cause of the undercut shape of the one side of the slot, this latter movement causes the cooperating end 5811" of the pawl to move down fully into the cam slot, as shown in Figure 16, this causing the other end 581) of the pawl to move down into the cooperating stop ring slot, as illustrated.

This small clockwise movement of all of the corresponding cams in the various units upon reversal of the drive causes an accurate synchronization of all of the selector means. Then, when another tuning cycle is initiated, the action of the spring 83 is so quick that a positive hightorque drive is provided within a few degrees of rotation of the driving part 8|. Even if one spring ratchet arrangement catches two degrees ahead of one in another unit, sufilciently accurate synchronization is maintained for proper all) 10 operation of the units. Moreover, any slight one or two degree difference is never cumulative, since all ofthe selector cam drums are properly and exactly synchronized upon each reversal of the drive during a tuning cycle. While not as positive as the drive connection arrangement first illustrated and described, a unit of the kind shown in Figures 10-16 has successfully operated through hundreds of test operations without any of its selector parts getting out of synchronization. In this form of drive arrangement there is never any decoupling of the spring 83, so that there is never any lost motion or waiting time during operation. This is of particular importance in a single turn arrangement; where the time length of a tuning cycle might be increased as much as 30 or 40% if the single tooth ratchet had to go through nearly a full revolution before its engagement.

While I have shown and described certain embodiments of my invention, it is to be understood that it is capable of many modifications. Changes, therefore, in the construction and arrangement may be made without departing from the spirit and scope of the invention as disclosed in the appended claims. I

I claim:

1. In apparatus for automatically positioning a shaft and having driving means so arranged that the shaft is first rotated in one direction until stopped at a terminalposition, and then rotated in the other direcion until stopped at a preselected position, the selection being eifected by a rotatable member adapted to be driven in only one direction, means for connecting the driving means and rotatable member, including: a rotatable driving part; a rotatable driven part, said parts having coaxial cylindrical surfaces; and frictionally operative means instantly providing driving connection between said parts upon rotation of the driving part in the first mentioned direction, this means comprising a helical spring at least partially wrapped around each of said surfaces. 7

2. In apparatus for automatically positioning a shaft and having driving means so arranged that the shaft is first rotated in one direction until stopped at a terminal position, and then rotated in the other direcion until stopped at a preselected position, the selection being effected by a rotatable member adapted to be driven in only one direction, means for connecting the driving means and rotatable member, including: a rotatable driving part; a rotatable driven part; frictionally operative means instantly providing driving connectionbetween said parts upon rotation of the driving part in the first mentioned direction; means for rendering said driving connection inoperative after a brief interval; and separate means adapted to provide a positively operative driving connection between said parts such that they have a predetermined relationship to each other.

3. In apparatu for automatically positioning a shaft and having driving means so arranged that the shaft is first rotated in one direction until stopped at a terminal position, and then rotated in the other direction until stopped at a preselected position, the selection being efiected by a rotatable member adapted to be driven in only one direction, means for connecting the driving means and rotatable member, including: a rotatable driving part; a rotatable driven part; frictionally operative means instantly providing driving connection between said parts upon rotation of the driving part in the first mentioned direction, this means transmitting only a small torque in the opposite direction; means for rendering said driving connection inoperative after a brief interval of rotation in said first mentioned direction; and positively operative ratchet means adapted to provide a driving connection between said parts, upon rotation of the driving part in the first mentioned direction, such that they have a predetermined relationship to each other.

4. Apparatus of the character claimed in claim 3, wherein the frictionally operative means comprises a spring cooperating with a cylindrical surface.

5. Apparatus of the character claimed in claim 3, wherein the positively operative means comprises a single-tooth ratchet.

6. In apparatus for automatically positioning a shaft and having driving means so arranged that the shaft is first rota-ted in one direction until stopped at a terminal position, and then rotated in the other direction until stopped at a preselected position, the selection being effected by a rotatable member adapted to be driven in only one direction, means for connecting the driving means and rotatable member, including: a rotatable cylindrical driving part; a rotatable cylindrical driven part concentric with the driving part; a helical spring encircling at least a part of bot of said parts and soarranged as to instantly provide frictional driving connection between said parts upon rotation of the driving part in the first mentioned direction; means for rendering said frictional driving connection inoperative after a brief interval of rotation in said first mentioned direction; and a single-tooth ratchet adapted to provide a driving connection between said parts, upon rotation of the driving part in the first mentioned direction, such that they have a predetermined relationship to each other.

'7. In apparatus for automatically positioning a shaft and having driving means so arranged that the shaft is first rotated in one direction until stopped at a terminal position, and then rotated in the other direction until stopped at a preselected position, the selection being effected by a rotatable member adapted to be driven in only one direction, means for connecting the driving means and rotatable member, including: a rotatable driving part; a rotatable driven part; frictionally operative means instantly providing driving connection between said parts upon rotation of the driving part in the first mentioned direction, but transmitting only a small torque in the opposite direction, this means comprising a spring mainly cooperating with a cylindrical surface, but with one end turned away from such surface; a

stop member for rendering said driving connection inoperative by engaging one ,end oi said spring after a brief interval of rotation in said first mentioned direction; and positively operative ratchet means adapted to provide a driving connection between said parts, upon rotation of the driving part in the first mentioned direction, such that they have a predetermined relationship to each other. I

8. In apparatus for automatically positioning a shaft and having driving means so arranged that the shaft is first rotated in one direction until stopped at a terminal position, and then rotatedin the other direction until stopped at a preselected position, the selection being effected by a rotatable member adapted to be driven in only one direction, means for connecting the driving means and rotatable member, including: a rotatable cylindrical driving part; a rotatable cylindrical driven part concentric with the driving part; a helical spring in the main body of which encircles at least a portion of both of said parts and is so arranged as to instantly provide frictional driving connection between said parts upon rotation of the driving part in the first mentioned direction, said spring having one end turned away from said parts; means for rendering said frictional driving connection inoperative after a brief interval of rotation in said first mentioned direction, this means comprising a stop member adapted to be engaged by one end of the spring; and a singletooth ratchet adapted to provide a driving connection between said parts, upon notation of the driving part in the first mentioned direction, such that they have a predetermined relationship to each other.

RICHARD W. MAY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Certificate of Correction Patent No.2,449,079. September 14, 1948.

RICHARD W. MAY

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Column 12, line 21, claim 8, after the Word spring strike out in; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Ofiice.

Signed and sealed this 23rd day of November, A. D. 1948.

THOMAS F. MURPHY, I

Assistant Commissioner of Patfits. 

